Starting to get a little narrow, but you could probably go down to about an 18mm tire on that rim before you had problems. If the 25s are OK then 2mm isn't enough to make things go sour.
–
Daniel R HicksJul 26 '13 at 21:12

Depends on the application. There is a very large difference aerodynamically depending on the rim shape and depth that the tire is paired with. Admittedly this is primarily a time trial consideration, but tire/rim selection can have dramatic impacts on Cda.
–
JohnPJul 26 '13 at 14:15

2

True of course - but I was answering in terms of fit.
–
Chris HJul 26 '13 at 14:46